Embodiments of the application relate generally to ultrasound imaging, and more specifically to an arrangement of a plurality of sub-arrays on a transducer array.
Conventional ultrasound imaging systems generally employ an array of transducer elements to transmit an ultrasound beam and subsequently receive a reflected beam from an object under interrogation. As will be appreciated, the array of transducer elements may include an arrangement in which the transducer elements are arranged in a two-dimensional array. Moreover, some ultrasound imaging systems may utilize large two-dimensional arrays of transducer elements often containing between 1000 and 20,000 transducer elements. Unfortunately, such a large number of transducer elements substantially exceeds the number of beamforming channels typically available even in most advanced ultrasound imaging systems.
Previously conceived methods for performing beamforming on such large arrays of transducer elements utilize configurable transducer arrays in which transducer elements having similar delays are grouped together. However, while the delays for the connected transducer elements may be similar, the delays may not be identical, thereby resulting in delay errors. In certain situations these delay errors may be within acceptable limits. However, as the number of transducer elements connected to a beamforming channel increases, the delay errors may become unacceptable. An alternative solution for applications that employ a large number of transducer elements is the use of sub-aperture processors (SAPs) to reduce the number of system channels required to process signals from the large number of transducer elements. However, use of the conventional SAPs may not provide the complete, dynamic delay required to beamform the signal.
Furthermore, currently available beamforming techniques propose altering the shape of the sub-apertures coupled to the sub-aperture processor as a function of the beam direction. As will be appreciated, altering of the shape of the sub-apertures involves changing the transducer elements that are connected as inputs to the sub-aperture processors. For example, the reconfigurable nature of the transducer element inputs imposes stricter requirements on the amplifiers which receive signals from the elements. Most notably, noise associated with switching inputs to the SAP may be amplified by the amplifier in the SAP, thereby necessitating use of very low noise switching. Also, the large impedance of the small transducer elements makes switching difficult. Furthermore, since the transducer elements are also used to transmit acoustic energy, the switches typically require high voltage, thus making the switch circuits large and less suitable for the application.